If you ask me, I would add some UMB card and an EMS card.
Like those cheap 8-Bit cards from Lo-tech or replicas from other manufacturers.
Provided that you're interested in late 80s/early 90s software or professional software.
Some utilities in MS-DOS 6.x can make use of EMS, whereas DOS itself can store parts of it in the UMA (640-1MB) and HMA (64KB minus 16Bytes above 1MB).
Of course, 8-Bit access slows things down.
The others surely will tell you about it no doubt.
They aren't wrong, but also not exactly right, either.
Thing is, back in the day, many 8-Bit ROM chips on older expansions cards
were not interleaved and connected via 8-Bit, anyway.
So it's no ideal by any means, but not murks either. It simply happened.
So if your HDD controller or ethernet card was calling a ROM routine, it ended up being 8-Bit at worst.
That's why "shadow memory" became a thing. It copied slow ROM code into fast RAM.
Same goes for older graphics cards or EMS boards sometimes.
Some AST (?) board models had a 16-Bit connector, but the transfers were 8-Bit really.
Heck, some ancient ISA VGA cards did their whole i/o via 8-Bit and people didn't notice back then. 😉
That's why I think to myself: Little keyboard/mouse drivers don't need much space or bandwidth, either.
But they make room for more demanding programs located in the conventional memory.
A single piece of, say, 1 to 64KB contiguous memory (as UMB) is just a single segment of memory to an old 8086, even.
The transfer should be fast enough to not hog the 8-Bit bus too long.
But I'm speaking under correction, of course.
I do merely have one 4,77MHz machine and my experience with 8-Bit PCs is still lacking.
My point is just: Slow memory is better than no memory, at all.
Plus, an 8MHz 80286 isn't exactly fast, anyway.
So I think it would be okay if it ends up being on a XT or Turbo XT level.
However, just don't spend too much money on 8-Bit expansion cards.
If you can get them at a reasonable price, they might be worth trying out.
That being said, if you're running MS/PC-DOS 3.30 then that's not needed perhaps.
Likewise, if your games/programs fit into 640KB, then everything is okay the way it is.
It's just if you're going to play MOD files, watch retro pictures etc. that memory will be a limiting factor quickly.
Good luck! 😀
Edit: Typos fixed.
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